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makekey - generate encryption key
Makekey improves the usefulness of encryption schemes depending on a key by increasing the
amount of time required to search the key space. It reads 10 bytes from its standard
input, and writes 13 bytes on its standard output. The output depends on the input in a
way intended to be difficult to compute (i.e. to require a substantial fraction of a sec-
The first eight input bytes (the input key) can be arbitrary ASCII characters. The last
two (the salt) are best chosen from the set of digits, upper- and lower-case letters, and
`.' and `/'. The salt characters are repeated as the first two characters of the output.
The remaining 11 output characters are chosen from the same set as the salt and constitute
the output key.
The transformation performed is essentially the following: the salt is used to select one
of 4096 cryptographic machines all based on the National Bureau of Standards DES algo-
rithm, but modified in 4096 different ways. Using the input key as key, a constant string
is fed into the machine and recirculated a number of times. The 64 bits that come out are
distributed into the 66 useful key bits in the result.
Makekey is intended for programs that perform encryption (e.g. ed and crypt(1)). Usually
its input and output will be pipes.
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